"Howdy! My name is Weenie_Butt. Weenie_Butt the flower!"
– Weenie's first appearance
Weenie_Butt, aka Weenie, is a flower with grey petals, and the first monster our protagonist meets.
Weenie uses cone-shaped attacks, dubbed "Friendliness Narwhal Horns", to attack our protagonist. He then proceeds to mumble that he needs to come up with a better name for them, inferring that this is his first time meeting a fallen.
This is later confirmed.
"In fact, I think that's the first human you greeted, isn't it?"
– Flowey in some strange psychological conversation with Weenie
This quote also shows that Weenie and Flowey are connected somehow. It also shows that they are extremely familiar with one another, as Weenie keeps calling Flowey Asriel.